The present invention relates to a lamp cooling device for cooling a lamp for use as a light source for projection display apparatus, and a projection display apparatus, and more particularly to a lamp cooling device for directly air-cooling an intralamp space surrounded by a reflector and a front transparent plate, and a projection display apparatus.
FIGS. 20 and 21 of the accompanying drawings show a structure of a general lamp 1 for use as a light source for projection display apparatus. The lamp 1 has a light emission source 3a including a glass tube filled with a discharge gas. The light emission source 3a is positioned in a space surrounded and sealed from the exterior by a reflector 2 and a front transparent plate 5. Light emitted from the light emission source 3a is reflected toward the front transparent plate 5 side by a reflecting surface as an inner surface of the reflector 2, and passes through the front transparent plate 5 out of the lamp 1. The light emitted from the lamp 1 is mainly composed of parallel rays of light as indicated by the solid-line arrows in FIG. 21. However, the light emitted from the lamp 1 may be converged or diverged as indicated by the broken-line arrows in FIG. 21.
The light emission source 3a radiates not only light, but also a large amount of heat. From the standpoint of better light emission efficiency and longer service life, the temperature Tb of the light emission source 3a (burner) and the temperature Tc of a sealed portion 3b of the bulb tip end need to fall in a predetermined temperature range. As shown in FIG. 20, it has been customary to cool the lamp 1 with cold air that is applied to the rear end of the lamp 1 by a fan 51.
To meet recent requirements for higher lamp luminance, the amount of heat to be discharged from the lamp is growing, making it difficult to keep the temperatures Tb, Tc within the predetermined temperature range simply by applying cold air to the lamp 1 as shown in FIG. 20. The temperatures Tb, Tc may be kept within the predetermined temperature range by increasing the rotational speed of the fan 51 or employing a larger fan. However, these proposals may possibly tend to produce air flow noise at a level not permissible for projection display apparatus, and greatly reduce the commercial value of projection display apparatus.
There has been proposed a structure as shown in FIG. 22 of the accompanying drawings wherein openings 52, 53 are defined respectively in lower and upper surfaces of a reflector 2 and the space in a lamp 1 is ventilated through the openings 52, 53 for thereby directly air-cooling a light emission source 3a and a sealed portion 3b of the bulb tip end. For details, reference should be made to Japanese Patent Laid-Open No. 10-186513 (FIG. 6B), for example.